The invention relates to an interspinal prosthesis with a central part having a central axis, which can be introduced into the interspinal space, an inner end and an outer end, as well as two processes, which arise at the outer end, the two processes extending radially and diametrically with respect to the central axis and which can be introduced into the space between the spinal processes of two adjacent vertebrae, a counterpart thereto as well as to a multi-part interspinal prosthesis combined therefrom.
Such prostheses function as spacers for two adjacent vertebrae in the case of a defective disk, which would otherwise reduce the distance between the vertebrae. The stress on the facet joints is also relieved by the enlarged distance.
W099/42051 discloses an interspinal prosthesis of this type, which includes a central piece, which is to be introduced into the interspinal space and from which a pair of ears arises cranially and caudially to the right and to the left of the central piece, in order to hold the central piece in the space between the spinous processes (processus spinosus) of two adjacent vertebrae after an implantation. A disadvantage of this known prosthesis is the fact that the latter is in one piece, which makes the implantation more difficult, so that it is necessary to remove the supraspinal ligament. The removal of this ligament has the disadvantage that the prosthesis is not held securely in the dorsal direction. For this reason, it is proposed in W099/42051 that the prosthesis be drilled through in the interspinal central piece, in order to pass a tape through the borehole, with which tape the prosthesis can be tied to the spinous processes of the adjacent vertebrae. This procedure is very time-consuming and complicated.
The above discussion of the state of the art is given only to explain the environment of the invention and does not mean that the cited state of the art was also actually published or publicly known at the time of this application or its priority.